The invention relates generally to quantum gates. In particular, the invention relates to shifting the quantum state of a photon along a path using weak measurement based on switchable introduction of a shutter.
Because quantum interference differs fundamentally from the interference phenomena of classical physics, this phenomenon has remained a continuing topic for discussion and debate since the early days of quantum theory. The essence of this difference is embodied in the two-slit experiment. From both the classical and Schrödinger wave perspectives, the resulting two slit interference pattern is easily described in terms of the overlapping contributions of the wave which have passed through each slit. The wave perspective also explains the disappearance of the interference pattern when one of the slits is closed.
However, interference experiments using low intensity electron or photon beams in which only one particle at a time passes through a two-slit apparatus have shown that the accumulated effect when both slits are open is an interference pattern like that produced by higher intensity ensembles and that the pattern disappears when one slit is closed, as described by A. Tonomura et al. in “Demonstration of single electron buildup of an interference pattern”, Am. J. Phys. 57 117-20 (1989).